The use of computers to collect and process data is widespread in virtually every phase of modern society. Computers can collect and process vast amounts of data ranging from accounting spreadsheets and databases to scientific and medical research. While vast amounts of raw data can be collected, processing and presenting the data in a meaningful fashion is often more difficult than the initial collection of the data. It is not uncommon that computers generate more data than can be processed by the person collecting the data. For example, it is possible to collect vast amounts of physiological data for a hospital patient. All of this data must be reviewed and analyzed by a physician or technician for the data to have any relevance to the patient.
The reduction of raw data to a more meaningful form is ever more important in such situations where the physician or technician must review the vast amount of data for a number of patients in the course of a normal workday. There are a variety of techniques known in the art for reducing raw data to a more meaningful form. One such method is the statistical analysis to reduce the raw data to one or more statistical numbers representative of the raw data.
Another technique used to reduce the data is to plot the data in some fashion that simplifies the interpretation of the data. One example of such a plot is termed a scatter-plot, which are sometimes referred to as Lorentz or Poincare plots. Scatter-plots are a powerful graphic tool that can be applied to raw data to reduce to data to a form that can be interpreted in a glance.
Scatter-plots have been used to plot electrocardiograph (ECG) data. In particular, research has shown that plotting the R--R interval of three successive heartbeats of the ECG can produce a useful form of ECG data that can be easily interpreted by the physician. The first R--R interval is the time between the R-waves of the first and second successive heartbeats, respectively, and the second R--R interval is the time between the R-waves of the second and third successive heartbeats, respectively. One R--R interval is plotted on a first axis and the second R--R interval is plotted on the second axis, as shown in FIG. 1.
Some prior art instruments use scatter-plots to display R--R intervals of ECG data to measure the heart rate variability (HRV). Research has shown that HRV is a useful measure of the health of the patient's cardiovascular system. These prior art systems have the limited capability to select which R--R intervals are the most appropriate to include in the scatter-plot. For example, there is only limited selection of the source of heartbeats, such as normal and ectopic heartbeats, that will be included in the scatter-plot. Similarly, prior art systems have limited ability to specify minimum or maximum R--R intervals that will be included in the scatter-plot. The result of such limitations is that data in the scatter-plot include information that is not useful to the physician. The additional data requires additional analysis time by the physician thus reducing the overall effectiveness of this form of graphic presentation.
Therefore, it can be appreciated that there is a great need for a system and method of presenting scatter-plot data in a manner that permits flexibility in the selection of analysis and display parameters. The present invention fulfills this need an provides other advantages as will become apparent from the detailed description.